> The test
> `serviceability/jvmti/GetOwnedMonitorInfo/GetOwnedMonitorInfoTest.java` is
> failing with the assert in the `thaw_internal()` function. The assert is not
> fully correct as it does not account for an unexpected scenario.
>
> Thanks to Patricio for reproducing this failure and identifying the root
> cause:
>> The problem is that we can unmount a virtual thread, then mount it again,
>> thaw a few frames, execute code that acquires a JNI monitor, and then call
>> thaw again without releasing that monitor. In this test this will happen if
>> the vthread is unmounted in System.out.println("Thread doing JNI call: "
>> ...) because of contention with the main thread doing
>> System.out.println("Main waiting for event.").
> The issue can be reproduced by adding Thread.yield() before
> jniMonitorEnterAndLetObjectDie().
>
> The fix corrects the assert to account for the `thread->jni_monitor_count()`.
> Question: Is the same scenario possible for non-JNI monitors as well?
> Also, the fix includes the test tweak described above which makes this
> failure always reproducible.
>
> Testing:
> - Ran the test `GetOwnedMonitorInfoTest.java` locally
> - Mach5 tiers 1-6 are passed
Serguei Spitsyn has updated the pull request incrementally with one additional
commit since the last revision:
added a comment explaining why extra yield is needed
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/20294/files
- new: https://git.openjdk.org/jdk/pull/20294/files/9c10c555..fc336bc2
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=20294&range=02
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=20294&range=01-02
Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
Patch: https://git.openjdk.org/jdk/pull/20294.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/20294/head:pull/20294
PR: https://git.openjdk.org/jdk/pull/20294
